Comparing atrocities is a profitless and cruel but still -- at times -- an important exercise, at least for some perspective. Rwanda was a comprehensive and directed genocide in which Hutus killed 10,000 Tutsis a day during three months in 1994. It wasn't a regime against rebels or a civil war; it was a systematic extermination.

No, Syria isn't Rwanda; and it's certainly not Barack Obama's primary responsibility. But does that mean the need to stop the killing -- 12,000 dead and counting -- is any less urgent and acute?

The issue, as always, is what to do. In policy matters -- as in life, people (and governments) -- are more frequently presented with imperfect options. Those abound in the case of Syria. Here is why they are imperfect:

Aaron David Miller

Sanctions and political isolation won't work quickly enough. A year in, the Assad regime has demonstrated that it can "manage," even as it faces a deteriorating economy and a pariah status. Aid from Iran helps it get by. As long as the regime keeps its military and security services happy, it might survive for quite some time.

Diplomacy has failed. The six-point peace plan brokered by United Nations envoy Kofi Annan — it called for a ceasefire and dialogue with the opposition, among other things -- can't succeed because it has no agreed-upon end state acceptable to the regime and the opposition. It's worth trying to get the Russians to walk away from the Assads, but this will not be easy.

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After all, the Russians have seen their former clients drop like pins in a bowling alley, all under American pressure -- Saddam Hussein, Moammar Gadhafi, now, perhaps, Bashar al-Assad-- and the United States is now asking them to press their Iranian friends on the nuclear issue, too. You'd have to satisfy Moscow that some regime elements would remain as part of any solution and give al-Assad immunity -- both tough to do.

Half measures don't answer the mail. These seem compelling and logical on paper. But in practice, half measures, such as arming the opposition and establishing safe zones, will not bring the desired result -- the toppling of the regime. The first is being done already -- quietly -- apparently with American support. But against the al-Assad regime you could never supply the kind and quantity of weapons necessary to turn the tide decisively against the regime's superior firepower; nor can we control to whom these arms are actually going. The proliferation of weapons and militias in post-Gadhafi Libya also points up the problem of unregulated,unsupervised arms flows.

Safe zones, secure areas along the Turkish border that could provide sanctuary for refugees and a base from which to equip and terrain rebel military forces, would require full buy-in by Turkey, which so far has been reluctant to intervene. They'd also have to be defended, lest we repeat the tragedy of Bosnia in 1995, where UN peacekeepers couldn't or wouldn't prevent Serbian massacres of Bosnian Muslims. The Russians and the Chinese would likely oppose them, too. And in the end, it's not at all clear how they would prevent the regime from continuing its repression and killing.

Military intervention: We need to be honest with ourselves. Unless we get lucky -- perhaps if there's an internal coup that takes out al-Assad or the Russians help pressure him -- only military intervention that directly weakens the regime and changes the balance of power on the ground will bring them down.

We need to be clear about what this might cost. There is no international mandate to sanction a military intervention (and there likely won't be given Russian/Chinese opposition). Syria isn't Libya; it has a sophisticated air defense system and stockpiles of chemical and biological weapons, and it's much more likely than in Libya that airstrikes and precision guided munitions alone won't do the job. Boots on the ground may be required, too.

If the president of the United States determines that toppling al-Assad is in the vital national interest of the United States, then he should craft a strategy to do it. My take is that it isn't, certainly not enough to justify a unilateral military intervention that could have the United States "owning" the country (see Afghanistan and Iraq).

It won't be on the cheap.

Indeed, the president also has to accept the possibility that what we break during a military campaign, we'll own and have responsibility for fixing. If al-Assad falls, the process of putting the Syrian Humpty-Dumpty together will make the Libyan experience look like Switzerland. And we could be right in the middle of the muddle.